Floating labyrinth or controlled gap seals are used in gas turbine engines, interstage compressors, refrigeration compressors, aircraft cabin compressors, jet engines, superchargers and missiles to provide a close tolerance seal around a rotating shaft. In these applications the floating labyrinth seal surrounds the shaft and functions to restrict access of hot gases, cryogens or other pressurized fluids to bearings and other structures surrounding the shaft.
Examples of prior art floating labyrinth seals are illustrated in a publication titled "Mechanical Seals for Rotating Shafts" published by Rexnord Corporation, the assignee of the present invention. As illustrated on pages 21-23 of that publication, such labyrinth seals commonly include a seal shell housing a labyrinth ring assembly, the ring assembly comprised of a carbon insert ring encased in a metal retaining band. The carbon insert ring includes an annular inner surface adapted to interface with the exterior surface of the shaft to restrict gas leakage along the surface of the shaft. It is critical that the labyrinth ring assembly be maintained nearly perfectly round in order to provide extremely close tolerance with the shaft to form a gas or fluid seal with the shaft and to accommodate very high speeds of rotation of the shaft. The shaft rotation speeds may be as high as 40,000 rpm and pressures on the labyrinth ring assembly may be as much as 2,000 psi. The effectiveness or stability of the labyrinth seal in such applications is directly related to the roundness of the inner surface of the carbon insert ring.
With prior art labyrinth ring assemblies it has been found that impact to the periphery of the metal retaining band or application of random low level energy to the metal band or carbon ring during assembly or handling can cause distortion of the ring assembly making the ring assembly useless in a seal application.